Carbon materials have been mainly used as adsorbents; at the same time, a wide range of applications are now being studied as they have fundamental properties including properties of electronic materials such as conductivity, high thermal conductivity, low thermal expansion coefficient, lightness and heat resistance. Recently, in particular, their properties of electronic materials have been attracting attention and these materials are used or considered to be used in the field of electronic materials such as negative electrodes of lithium ion secondary batteries and electrodes for capacitors.
Such carbon materials are conventionally produced by carbonization treatment using coconut husk, coal coke, coal or petroleum pitch, furan resin or phenol resin as a raw material.
In recent years, attempts are made to expand and develop the properties of carbon materials by adding another element to carbon materials. Under the circumstances, nitrogen-containing carbon materials are reported to improve electrochemical properties when used for applications such as negative electrodes of lithium ion secondary batteries and electrodes for capacitors (see, for example, Patent Documents 1, 2). Nitrogen-containing carbon materials have also drawn attention as they are reported to have properties of adsorbents (see, for example, Patent Document 3) and hydrogen storage materials (see, for example, Patent Documents 4, 5).
Processes for producing a nitrogen-containing carbon material and nitrogen-containing carbon materials which are conventionally known are cited below.
As the processes for producing a nitrogen-containing carbon material, (1) a process in which a low molecular weight nitrogen-containing organic compound is chemically vapor-deposited (CVD) as a raw material and (2) a process in which a low molecular weight nitrogen-containing organic compound is polymerized as a raw material and the resulting resin is subjected to carbonization are mainly known.
As the aforementioned process (1), for example, a process in which a nitrogen-containing organic compound such as pyrrole is deposited on a substrate (see Patent Documents 6, 7), a process in which such a compound is deposited in the pore of a porous material (see Patent Document 3), a process in which an acyclic organic compound such as acetonitrile is deposited on a carbon material (see Patent Documents 8, 5) and a process in which 2,3,6,7-tetracyano-1,4,5,8-tetraazanaphthalene is polymerized and carbonized at a high temperature (see Patent Document 9) are known.
As the aforementioned process (2), for example, a process in which a melamine resin, an urea resin or an aniline resin is carbonized at a high temperature (see Patent Document 10), a process in which polyimide is carbonized at a high temperature (see Patent Document 1), a process in which polyaniline is carbonized at a high temperature (see Patent Document 2), a process in which polypyrrole is carbonized at a high temperature (see Patent Document 11), a process in which phthalocyanine is mixed with a precursor of a furan resin and the mixture is carbonized at a high temperature (see Patent Document 12) and a process in which polyacrylonitrile is carbonized at a high temperature (see, for example, Patent Document 13) are known.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-80914
[Patent Document 2] Japanese Patent Application Laid-Open No. 10-21918
[Patent Document 3] Japanese Patent Application Laid-Open No. 2004-168587
[Patent Document 4] Japanese Patent Application Laid-Open No. 2005-798
[Patent Document 5] Japanese Patent Application Laid-Open No. 2003-277026
[Patent Document 6] Japanese Patent Application Laid-Open No. 7-90588
[Patent Document 7] Japanese Patent Application Laid-Open No. 9-27317
[Patent Document 8] Japanese Patent Application Laid-Open No. 2004-342463
[Patent Document 9] Japanese Patent Application Laid-Open No. 2003-137524
[Patent Document 10] Japanese Patent Application Laid-Open No. 2000-1306
[Patent Document 11] Japanese Patent Application Laid-Open No. 8-165111
[Patent Document 12] Japanese Patent Application Laid-Open No. 2004-362802
[Patent Document 13] Japanese Patent Application Laid-Open No. 8-180866
[Patent Document 14] Japanese Patent Application Laid-Open No. 2005-239456